Technical Field
The present invention relates to an ultrasonic device, an ultrasonic probe, an ultrasonic diagnostic apparatus, and a method of manufacturing an ultrasonic device.
Related Art
Ultrasonic devices for transmitting and receiving ultrasonic waves have been widely used in ultrasonic diagnostic apparatuses and the like. Then, generally used in an ultrasonic device is a vibrator where electrodes are formed at both ends of a piezoelectric body of, inter alia, a piezoelectric ceramic, of which lead (Pb) zirconium titanate (PZT) is representative. Japanese Laid-Open Patent Publication No. 1-12-49640 discloses such an ultrasonic device. According thereto, ultrasonic devices have different thicknesses of PZT installed on a substrate, where there are stepped differences. Vibrators of low resonant frequency are installed on the lower stages, and vibrators of high resonant frequency are installed on the upper stages.
Then, an acoustic matching layer is arranged so as to overlap the respective vibrators. Where the opposite side of the vibrators is understood to be the front surface, the acoustic matching layer has a front surface that is formed so as to be flat. Having a flat front surface makes it possible to easily make contact with a test subject. The thickness of the acoustic matching layer and the thickness of the vibrators are set so as to correspond to the resonant frequency. The difference in length found by adding both the thickness of the acoustic matching layer and the thickness of the vibrators will be the height of the stepped differences of the substrate. As such, providing the stepped differences to the substrates makes it possible to properly set both the lengths of the vibrators and the length of the acoustic matching layer even though the front surface is a flat one.